Assessment of Cerebrovascular Dynamics and Cognitive Function with Acute Aerobic Exercise in Persons with Multiple Sclerosis.

BACKGROUND: Cognitive dysfunction in multiple sclerosis (MS) may partially stem from inadequate cerebral blood flow. Cerebral blood flow and cognitive function improve with aerobic exercise in healthy adults. The effect of aerobic exercise on cerebrovascular hemodynamics and cognitive performance in persons with MS is unclear. The acute effect of aerobic exercise versus quiet rest on cerebrovascular hemodynamics and cognitive performance in relapsing-remitting MS was examined. METHODS: Sixteen adults with relapsing-remitting MS underwent cerebrovascular hemodynamics and cognitive performance testing before, 2 minutes after, and 30 minutes after aerobic exercise (20-minute treadmill walking, 60% peak oxygen consumption) and a time-matched seated control. Brachial blood pressure was obtained via an oscillometric cuff. Right middle cerebral artery (MCA) blood velocity was measured via transcranial Doppler and used to calculate mean velocity, pulsatility index (PI), and conductance. Carotid artery stiffness was measured via ultrasonography and tonometry. Cognitive performance (accuracy, reaction time) was assessed using a modified flanker task. RESULTS: Exercise elicited significant increases in mean pressure and carotid artery stiffness and decreases in MCA conductance at 2 minutes after exercise, which subsided by 30 minutes (P < .05). Exercise did not significantly alter MCA PI. Flanker reaction time decreased during posttesting in both conditions (P < .05). There were no condition × time interactions for cognitive performance. CONCLUSIONS: Persons with MS seem resilient to exercise-induced acute changes in MCA PI despite transient carotid stiffening, potentially via reductions in MCA conductance. These data suggest that changes in cognitive performance after acute aerobic exercise are not directly related to transient cerebrovascular responses in persons with MS.

Hemodynamic Response to Isometric Handgrip Exercise in Adults with Intellectual Disability.

INTRODUCTION: Individuals with intellectual disability (ID) have an increased risk of cardiovascular disease and reduced work capacity, which could partly be explained by alterations to autonomic and hemodynamic regulation. The measurement of heart rate and blood pressure during isometric handgrip (HG) exercise, a sympathoexcitatory stimulus, is a noninvasive method to investigate autonomic and hemodynamic alterations. The purpose of this study was to assess alterations to autonomic and associated hemodynamic regulation between individuals with ID and a matched control group during isometric HG exercise. METHODS: Individuals with ID (n = 13; 31 ± 2 yr, 27.6 ± 7.7 kg·m-2) and without ID (n = 16; 29 ± 7 yr, 24.2 ± 2.8 kg·m-2) performed 2 min of isometric HG exercise at 30% of maximal voluntary contraction (MVC) in the seated position. Blood pressure was averaged for 2 min before, during, and after HG exercise (mean arterial pressure [MAP], systolic blood pressure, and diastolic blood pressure). Heart rate variability, blood pressure variability, and baroreflex sensitivity were calculated from the continuous blood pressure and heart rate recordings. RESULTS: Isometric HG elicited a blunted response in systolic blood pressure, diastolic blood pressure, and MAP among individuals with ID compared with individuals without ID, even after controlling for strength (MAP: rest, HG, recovery; ID: 103 ± 7, 108 ± 9, 103 ± 7; without ID: 102 ± 7, 116 ± 10, 104 ± 10 mm Hg; interaction P < 0.05). Individuals with ID also had an attenuated baroreflex sensitivity response to HG exercise compared with individuals without ID (interaction P = 0.041), but these effects were no longer significant after controlling for maximal voluntary contraction. Indices of heart rate variability and blood pressure variability were not different between groups overall or in response to HG exercise (P > 0.05). CONCLUSIONS: Individuals with ID have a blunted hemodynamic and autonomic response to isometric HG exercise compared with individuals without ID.

Aging reduces cerebral blood flow regulation following an acute hypertensive stimulus.

Aging increases arterial stiffness, which has a negative impact on cerebral blood flow (CBF) regulation (decreases CBF and increases CBF pulsatility). The association between arterial stiffness and CBF pulsatility may, in part, explain the relationship between elevated blood pressure (BP) fluctuations and end-organ disease with aging. To understand the mechanisms by which large BP alterations influence cerebral blood flow regulation in both young and old, we examined the effects of age on central and cerebral blood flow regulation following an acute hypertensive stimulus [resistance-exercise (RE)]. Measurements were obtained pre and immediately, 5, and 30 min post-RE in young (n = 35) and older (n = 26) adults. Measurements included cerebral blood velocity (CBv), CBv pulsatility, central pulse-wave velocity (PWV), beta-stiffness index (ß), and carotid blood flow pulsatility. Central hemodynamics and BP were continuously recorded. Mean CBv increased immediately post-RE only in the young and decreased below baseline at 5 min post-RE in both groups (interaction, P < 0.05). Older adults had a greater increase in CBv pulsatility immediately post-RE compared with the young (interaction, P < 0.05). Mean BP was higher and carotid pulsatility was lower in the older group and increased immediately post-RE in both groups (P < 0.05). PWV increased immediately post-RE (P < 0.05). There were no changes in ß. In conclusion, with aging, greater central arterial stiffness leads to a greater transmission of pulsatile blood velocity from the systemic circulation to the cerebral circulation following an acute hypertensive stress.NEW & NOTEWORTHY Reductions in cerebral blood flow and increases in flow pulsatility with aging are associated to cerebrovascular disease; however, little is known about how an acute hypertensive stimulus effects cerebral blood flow regulation in an aged population. Following the hypertensive stimulus, older adults elicit an attenuated increase in cerebral blood velocity and greater transmission of pulsatile velocity to the brain compared with young adults, demonstrating reduced cerebral blood flow regulation to elevated blood pressure responses with aging.

Hypertension in Adults With Intellectual Disability: Prevalence and Risk Factors.

INTRODUCTION: Individuals with intellectual disability have a high prevalence of obesity and low physical activity levels, which are risk factors for hypertension. This study estimated the prevalence of hypertension in a global data set of adults with intellectual disability participating in Special Olympics and investigated the role of physical activity and obesity in hypertension risk. METHODS: A total of 33,122 individuals aged ≥18 years with intellectual disability who participated in Special Olympic events from 2014 to 2018 had their brachial blood pressure, BMI, and self-reported physical activity assessed. Hypertension was classified using 2017 American College of Cardiology/American Heart Association guidelines (systolic blood pressure≥130 mmHg and diastolic blood pressure≥80 mmHg). Data were analyzed in 2019. RESULTS: Participants were aged 31 (SD=11) years, 64% male, and had a resting blood pressure of 121 (SD=16)/76 (SD=12) mmHg. The population was 48% (95% CI=47.5%, 48.6%) hypertensive. Male participants had a higher prevalence of hypertension (50.7%, 95% CI=50.1%, 51.4%) than female participants (43.1%, 95% CI=42.2%, 44.0%), with prevalence increasing with age. Odds of hypertension increased when performing no or insufficient physical activity and with increasing obesity (p<0.01), tripling (OR=3.06, 3.66) for all individuals who performed no physical activity except for those of normal weight (OR=1.72), and doubling (OR=2.13-3.87) for individuals who were obese or morbidly obese across all physical activity levels. CONCLUSIONS: This study is the first to determine population-based prevalence rates of hypertension in individuals with intellectual disability. It highlights the similarity in prevalence to the general population. The results emphasize the importance of population-wide screening, increasing physical activity, and reducing obesity in decreasing cardiovascular risk in this population.

Similar Effects of Acute Resistance Exercise on Carotid Stiffness in Males and Females.

Sex differences exist in vascular responses to blood pressure perturbations, such as resistance exercise. Increases in aortic stiffness following acute resistance exercise appear different between sexes, with attenuated increases in females vs. males. Whether sex differences exist in carotid stiffness, following resistance exercise is unknown. This study sought to examine sex differences in carotid stiffness, aortic stiffness, and hemodynamics following acute resistance exercise. Thirty-five participants (18 male) completed 3 sets of 10 repetitions of maximal isokinetic knee extension/flexion. Aortic stiffness and hemodynamics were estimated using an automated oscillometric blood pressure monitor at baseline, 5- and 30-min post-exercise. Carotid stiffness was assessed by ß-stiffness index, pressure-strain elastic modulus and arterial compliance using ultrasonography. Resistance exercise increased aortic stiffness, mean and systolic pressure at 5-min (p<0.01), and pressure-strain elastic modulus at 5-min in both sexes (p<0.05). Arterial compliance decreased at 5- and 30-min post exercise in both sexes (p<0.01). No interaction effects were detected in carotid stiffness, aortic stiffness, and hemodynamics, indicating similar vascular responses between sexes. Our findings indicate that the large arteries appear to stiffen similarly following resistance exercise in males and females when presented with similar blood pressure responses.

Physical activity and peak oxygen consumption are associated with walking in multiple sclerosis.

INTRODUCTION: Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system with a prevalence of nearly 1 million adults in the United States. MS results in declines in physical activity and peak oxygen consumption that might be independently associated with declines in walking performance. Therefore our purpose was to evaluate the association between physical activity and peak oxygen consumption with walking performance in individuals with MS. METHODS: Fifty individuals with MS between the ages of 18-70 yrs. (Female: 38; 46  ±  12 yrs.; BMI: 28.5  ±  6.4; EDSS: 3.3 [IQR: 2.5-4]) performed a maximal incremental cycle test to assess peak oxygen consumption (VO2peak), and wore an accelerometer for one week to measure moderate-to-vigorous physical activity (MVPA). Subjects further completed a timed 25-foot walk test (T25FW) and 6-minute walk (6MW) to measure walking performance. RESULTS: MVPA and VO2peak were correlated with 6MW and T25FW (p < 0.05). When combined in multivariate regression analyses, VO2peak and MVPA were both significant contributors of T25FW speed and 6MW, but after controlling for sex and age, MVPA was the only significant contributor (ß = 0.32 and ß = 0.44, respectively). CONCLUSION: Both higher MVPA and VO2peak were associated with better walking performance and in a combined model physical activity, but not peak oxygen consumption, remained an independent contributor to walking performance in individuals with MS. These results suggest that improving MVPA is a potential target for interventions to improve walking performance in persons with MS.

No effect of fitness on brachial or forearm vascular function during acute inflammation in young adults.

Acute inflammation is associated with increased risk of cardiovascular events and impaired vasodilatory capacity. Vasodilatory capacity can be measured in different segments of the arterial tree; however, it is unknown if the effects of acute inflammation are vascular segment-specific or if inflammation-induced dysfunction can be attenuated by factors that modulate cardiovascular risk, such as high cardiorespiratory fitness. The purpose of this study was to determine the effect of acute inflammation and fitness on conduit artery, resistance artery, and microvascular function in healthy, young adults. Vascular function was assessed at baseline and 24 h after a typhoid vaccination in 11 low-fit (5 male, 24 yr of age, 34.5 ± 2.9 ml·kg-1·min-1 peak O2 uptake (V̇o2peak)] and 12 high-fit (7 male, 27 yr of age, 56.4 ± 9.7 ml·kg-1·min-1 V̇o2peak) young adults. Vascular assessments included flow-mediated dilation (FMD) of the brachial artery, forearm reactive hyperemia (RH) via venous occlusion plethysmography, and near-infrared spectroscopy (NIRS) during a 5-min arterial occlusion. Acute inflammation was evident with increases in IL-6 and C-reactive protein (P < 0.01), and mean arterial pressure did not change (P = 0.33). FMD was lower in the high-fit group, yet it was reduced in both groups at 24 h, even after controlling for shear (P < 0.05). No effect of acute inflammation was observed for RH or NIRS (P > 0.05). Acute inflammation had nonuniform effects on vascular function throughout the arterial tree in young adults, and fitness did not alter the vascular response. This suggests that cardiorespiratory fitness may not protect the vasculature during acute inflammation in young adults in the absence of age- or disease-related decline in vascular function.

Acute systemic inflammation reduces both carotid and aortic wave reflection in healthy adults.

Acute inflammation increases the risk of cardiac and cerebrovascular events, possibly related to alterations in the hemodynamic load. Wave reflection at the aorta and carotid provides insight into downstream vascular changes and hemodynamic load at the heart and brain. Acute inflammation has been suggested to reduce wave reflection via downstream vasodilation; however, this is not firmly established and has only been investigated at the aorta. We sought to explore the effect of acute inflammation on aortic and carotid hemodynamics in healthy, young adults. Pressure waveforms were collected via radial and carotid applanation tonometry in 23 adults (26 ± 4 years) before and 24 h after a typhoid vaccination. Waveforms were calibrated to brachial mean and diastolic pressure, and waveform separation analyses (WSA) were performed, yielding augmentation index, reflection index, time to reflection (Tr), forward (Pf) and reflected (Pb) wave magnitude, and pulse wave velocity. Arterial diameters and carotid stiffness were measured via ultrasonography. Acute inflammation reduced wave reflection at 24 h in both the aorta and carotid (P < 0.05) without changes in mean pressure. WSA did not reveal independent changes in Pf, Pb, or Tr (P > 0.05). Arterial stiffness did not change; however, brachial and carotid artery diameters increased. Acute inflammation reduces wave reflection in the aorta and carotid artery in young adults, potentially due to downstream/peripheral vasodilation. Reduced aortic wave reflection did not disturb the cardiac workload; however, reductions in carotid wave reflection may render the brain vulnerable to pulsatile hemodynamics. These findings may have implications for cardiac and cerebrovascular risk during acute inflammation.

Preserved ability to blunt sympathetically-mediated vasoconstriction in exercising skeletal muscle of young obese humans.

Sympathetic vasoconstriction is attenuated in exercising muscles to assist in matching of blood flow with metabolic demand. This "functional sympatholysis" may be impaired in young obese individuals due to greater sympathetic activation and/or reduced local vasodilatory capacity of both small and large arteries, but this remains poorly understood. We tested the hypothesis that functional sympatholysis is impaired in obese individuals compared with normal-weight counterparts. In 36 obese and normal-weight young healthy adults (n = 18/group), we measured forearm blood flow and calculated forearm vascular conductance (FVC) responses to reflex increases in sympathetic nerve activity induced by lower body negative pressure (LBNP) at rest and during rhythmic handgrip exercise at 15% and 30% of the maximal voluntary contraction (MVC). FVC was normalized to lean forearm mass. In normal-weight individuals, LBNP evoked a decrease in FVC (-16.1 ± 5.7%) in the resting forearm, and the reduction in FVC (15%MVC: -8.1 ± 3.3%; 30%MVC: -1.0 ± 4.0%) was blunted during exercise in an intensity-dependent manner (P < 0.05). Similarly, in obese individuals, LBNP evoked a comparable decrease in FVC (-10.9 ± 5.7%) in the resting forearm, with the reduction in FVC (15%MVC: -9.7 ± 3.3%; 30%MVC: -0.3 ± 4.0%) also blunted during exercise in an intensity-dependent manner (P < 0.05). The magnitude of sympatholysis was similar between groups (P > 0.05) and was intensity-dependent (P < 0.05). Our findings suggest that functional sympatholysis is not impaired in young obese individuals without overt cardiovascular diseases.

Effect of acute maximal exercise on vasodilatory function and arterial stiffness in African-American and white adults.

INTRODUCTION: African-Americans are at increased risk of cardiovascular disease compared with their white counterparts, potentially due to greater arterial stiffness and reduced vasodilatory capacity. Racial differences also exist in arterial stiffness and blood pressure (BP) following maximal aerobic exercise; African-Americans do not exhibit central post exercise BP reductions. Whether impaired vasodilatory function contributes to the lack of BP response is unknown. PURPOSE: To evaluate vasodilatory function, arterial stiffness, and hemodynamics following a maximal aerobic exercise test in young, healthy African-American and white adults. METHODS: Twenty-seven African-American and 35 white adults completed measures at baseline, 15 and 30 min after a maximal exercise test. Measures included vasodilatory capacity of forearm resistance arteries, central pulse wave velocity (PWV), and carotid artery stiffness (ß). RESULTS: Forearm reactive hyperemia was greater in white but increased similarly following exercise in both groups (P < 0.05). Carotid ß-stiffness increased at 15 and 30 min (P = 0.03) in both groups, but PWV controlled for mean arterial pressure decreased after maximal exercise (P = 0.03). White exhibited reductions in systolic and mean pressure, whereas no changes were seen for African-Americans (interaction effects: P < 0.05). CONCLUSION: African-American and white adults had similar decreases in PWV, increases in ß-stiffness, and increases in vasodilatory function following maximal exercise. African-American adults, however, did not display reductions in BP and had overall lower vasodilatory function in comparison with white adults. Our results suggest African-Americans exhibit similar vasodilatory function changes following aerobic exercise as their white counterparts, and therefore vasodilatory function likely does not explain the lack of BP response in African-Americans.

Cardiopulmonary Profile of Individuals with Intellectual Disability.

INTRODUCTION: Individuals with intellectual disabilities (ID) are often sedentary and have low fitness levels. Current knowledge supports the existence of physiological barriers resulting in low fitness and exercise intolerance in individuals with Down syndrome, which might be applicable to other ID etiologies. If physiological barriers exist in ID, this would require adaptation of the physical activity guidelines. PURPOSE: The aim of this study was to assess differences in cardiopulmonary profiles, including maximal oxygen uptake, during a cardiopulmonary exercise test in individuals with ID without Down syndrome and healthy controls. METHODS: Participants performed an incremental cardiopulmonary exercise test on a treadmill until exhaustion. Outcomes were peak heart rate (HRpeak), absolute peak oxygen uptake (V˙O2peak), relative V˙O2peak, peak minute ventilation, peak CO2 expenditure, oxygen uptake efficiency slope, V˙E/V˙CO2 slope, absolute O2 pulse, relative O2 pulse, difference from predicted HRpeak, HR reserve, RERpeak, ventilatory threshold (VT), and VT as a percentage of V˙O2peak. Differences between groups were analyzed with Student's t-tests and multiple linear regression after adjusting for potential confounders (sex, age, body mass index, and activity level). RESULTS: Individuals with ID had worse outcomes on all of the cardiopulmonary outcomes, except for VT expressed as a percentage of V˙O2peak and V˙E/V˙CO2 slope (P < 0.05). Having ID was an independent predictor of reduced physiologic function during exercise (P < 0.05). CONCLUSION: These results demonstrate that individuals with ID present exercise intolerance potentially related to lower HRpeak and impairments in ventilatory function, and these results also suggest the possibility of peripheral muscle hypoperfusion. Existing physical activity guidelines likely underestimate the actual intensity of activity performed by individuals with ID and need to be adapted.

Comparative effectiveness of aerobic, resistance, and combined training on cardiovascular disease risk factors: A randomized controlled trial.

Although exercise has well-documented health benefits on cardiovascular disease (CVD), the benefit of combination exercise on CVD risk factors in individuals with elevated risk has not been fully elucidated. We compared the effects of aerobic, resistance, and a combination of both aerobic and resistance training on CVD risk factors including peripheral and central BP, cardiorespiratory fitness (CRF), muscular strength, body composition, blood glucose and lipids. Sixty-nine adults (58±7 years) with an elevated blood pressure or hypertension, overweight/obesity, and sedentary lifestyle were randomized to one of the three 8-week exercise programs or a non-exercise control group. Participants in all three exercise groups had an equal total exercise time, 3 days/week (aerobic: 60 minutes/session vs. resistance: 60 minutes/session vs. combination: aerobic 30 minutes/session plus resistance 30 minutes/session). Combined training provided significant reductions in peripheral (-4 mmHg) and central diastolic BP (-4 mmHg), increase in CRF (4.9 ml/kg/min), increase in upper (4 kg) and lower (11 kg) body strength, and increase in lean body mass (0.8 kg) (p <0.05). Aerobic training only increased CRF (7.7 ml/kg/min), and reduced body weight (-1.0 kg) and fat mass (-0.9 kg) (p <0.05). Resistance training only increased lower body strength (13 kg) and reduced waist circumference (-1.7 cm) (p <0.05). However, neither aerobic or resistance training alone showed significant reductions in BP (p>0.05). Furthermore, a composite score of CVD risk factors indicated a greater reduction with combination training compared to the control group. In conclusion, among individuals at an increased risk for CVD, as little as 8-weeks of combined training may provide more comprehensive CVD benefits compared to time-matched aerobic or resistance training alone.

Measures of adiposity differentially correlate with C-reactive protein among persons with multiple sclerosis.

BACKGROUND: While MS is considered, in part, an inflammatory disease, the relationship between measures of adiposity and MS have not been well studied. This is important considering the strength of the association between adiposity and inflammation reported in the general population, and the resultant increased risk for cardiovascular and metabolic disease. Evidence demonstrates MS is associated with higher prevalence rates of cardiovascular disease than the general population, which provides an impetus to examine how measures of adiposity and systemic inflammation are related in individuals with MS. OBJECTIVE: To examine the association between measures of adiposity and systemic inflammation, specifically using the global marker C-reactive protein (CRP), among persons with MS compared with a control group without MS. METHODS: Persons with MS and a control group (n = 33/group) had measures of adiposity (body mass index, total body fat, and trunk fat) correlated and regressed to CRP. RESULTS: Differential relationships between CRP and adiposity measures were observed between the MS group and the control group. Within the MS group, when adjusted for sex, age, and physical activity level, only whole body percent fat explained a significant portion of the variance in CRP (adjusted R2 = 0.095, p < 0.05), whereas all of the adiposity measures explained a significant degree of variance within the control group (p < 0.05), with trunk fat mass having the strongest correlation. CONCLUSIONS: The differential relationships observed between the MS and control groups suggests that whole body fat may be a more important factor related to whole body inflammation in MS, rather than other adiposity markers, such as BMI or trunk fat. This differential association should be taken into account in future research examining body fatness/obesity and CRP.

Influence of fitness and age on the endothelial response to acute inflammation.

NEW FINDINGS: What is the central question of the study? What are the effects of age and fitness on the vascular response to acute inflammation in younger and older adults? What is the main finding and its importance? In older adults, cardiorespiratory fitness level has a differential impact on endothelial function after acute inflammation. Compared with older adults with low fitness, older, moderately fit adults have a greater decrease in endothelial function, similar to that of younger adults. These findings have important implications in support of the beneficial effects of higher cardiorespiratory fitness in maintaining vascular reactivity and the ability to respond to stressors. ABSTRACT: Inflammation is associated with greater risk of cardiovascular events and reduced vascular function with ageing. Higher cardiorespiratory fitness is associated with lower risk of cardiovascular events and better vascular function. We evaluated the role of fitness in the vascular response to acute inflammation in 26 younger adults (YA) and 62 older adults (OA). We used an influenza vaccine to induce acute inflammation. Blood pressure, flow-mediated dilatation (FMD), augmentation index, carotid elastic modulus and inflammatory markers were measured before and 24 h after vaccination. Peak oxygen uptake was measured via a treadmill test. 'Fit' was defined as a peak oxygen uptake greater than the age- and sex-determined 50th percentile according to the American College of Sports Medicine. An interaction effect existed for the FMD response during acute inflammation (P < 0.05). The YA (low fit, from 11.5 ± 1.8 to 9.2 ± 1.3%; moderately fit, from 11.9 ± 0.8 to 9.0 ± 0.8%) and moderately fit OA (from 7.5 ± 1.0 to 3.9 ± 0.8%) had similar reductions in FMD at 24 h (P < 0.05). Low-fit OA did not reduce FMD at 24 h (from 5.5 ± 0.4 to 5.2 ± 0.5%, P > 0.05). The reduction in FMD in YA was similar between fitness groups (P > 0.05). All groups had similar reductions in mean arterial pressure and increases in inflammatory markers. The augmentation index and carotid elastic modulus did not change during acute inflammation. In conclusion, in OA, higher fitness is associated with a greater decrease in endothelial function during acute inflammation, and this response is similar to that of young adults. This suggests that moderately fit OA may maintain vascular reactivity in response to stress, indicating preserved vascular function in moderately fit versus low-fit OA.

Peripheral blood flow regulation in response to sympathetic stimulation in individuals with Down syndrome.

BACKGROUND: Individuals with Down syndrome (DS) experience autonomic dysfunction, with reduced sympathetic and parasympathetic control. This results in alterations in resting heart rate and blood pressure and attenuated responses to sympathoexcitatory stimuli. It is unknown to what extent this impacts the regulation of peripheral blood flow in response to sympathetic stimuli, which is an important prerequisite to exercise and perform work. Therefore, we aimed to investigate differences in peripheral blood flow regulation in response to lower body negative pressure (LBNP) between individuals with and without DS. METHODS: Participants (n=10 males with DS and n=11 male controls, mean age 23.7 years ± 3.2) underwent 5 min of LBNP stimulations (-20 mmHg), after resting supine for 10 min. One minute steady state blood pressure and blood flow at baseline and during LBNP were obtained for analysis. Mean flow velocity and arterial diameters were recorded with ultrasonography; foreram blood flow (FBF), shear rate and forearm vascular conductance (FVC) were calculated using brachial blood pressure measured right before ultrasound recordings. RESULTS: Participants with DS responded differently (consistent with reduced vasoconstrictive control) to the LBNP stimulus (significant ConditionxGroup interaction effect) for mean velocity (p=0.02), FBF (p=0.04), shear rate (p=0.02) and FVC (p=0.03), compared to participants without DS. CONCLUSION: Young males with DS exhibit reduced peripheral regulation of blood flow in response to LBNP compared to controls, indicating a blunted sympathetic control of blood flow. Further research is necessary to explore the impact of these findings on exercise and work capacity.

Effect of upper body position on arterial stiffness: influence of hydrostatic pressure and autonomic function.

OBJECTIVE: To evaluate changes in arterial stiffness with positional change and whether the stiffness changes are due to hydrostatic pressure alone or if physiological changes in vasoconstriction of the conduit arteries play a role in the modulation of arterial stiffness. METHODS: Thirty participants' (male = 15, 24 ±â€Š4 years) upper bodies were positioned at 0, 45, and 72° angles. Pulse wave velocity (PWV), cardio-ankle vascular index, carotid beta-stiffness index, carotid blood pressure (cBP), and carotid diameters were measured at each position. A gravitational height correction was determined using the vertical fluid column distance (mmHg) between the heart and carotid artery. Carotid beta-stiffness was calibrated using three methods: nonheight corrected cBP of each position, height corrected cBP of each position, and height corrected cBP of the supine position (theoretical model). Low frequency systolic blood pressure variability (LFSAP) was analyzed as a marker of sympathetic activity. RESULTS: PWV and cardio-ankle vascular index increased with position (P < 0.05). Carotid beta-stiffness did not increase if not corrected for hydrostatic pressure. Arterial stiffness indices based on Method 2 were not different from Method 3 (P = 0.65). LFSAP increased in more upright positions (P < 0.05) but diastolic diameter relative to diastolic pressure did not (P > 0.05). CONCLUSION: Arterial stiffness increases with a more upright body position. Carotid beta-stiffness needs to be calibrated accounting for hydrostatic effects of gravity if measured in a seated position. It is unclear why PWV increased as this increase was independent of blood pressure. No difference between Methods 2 and 3 presumably indicates that the beta-stiffness increases are only pressure dependent, despite the increase in vascular sympathetic modulation.

Associations of Health Club Membership with Physical Activity and Cardiovascular Health.

INTRODUCTION: This study evaluates whether a health club membership is associated with meeting the US physical activity (PA) guidelines and/or favorable cardiovascular health. METHODS: Using cross-sectional data of health club members (n = 204) and non-members (n = 201) from April to August 2013, this is the first study to our knowledge to examine a health club membership in relation to objectively measured cardiovascular health indicators including resting blood pressure, resting heart rate, body mass index, waist circumference, and cardiorespiratory fitness based on a non-exercise test algorithm. To determine the total PA and sedentary time, this study used a comprehensive PA questionnaire about both aerobic and resistance activities at the health club, as well as lifestyle activities in other settings, which was developed based on the International Physical Activity Questionnaire (IPAQ). RESULTS: The odds ratios (95% confidence interval) of meeting either the aerobic, resistance, or both aerobic and resistance PA guidelines for members compared to non-members were 16.5 (9.8-27.6), 10.1 (6.2-16.3), and 13.8 (8.5-22.4), respectively. Significant associations of health club membership with more favorable cardiovascular health outcomes and sedentary behavior were observed for resting heart rate (B: -4.8 b/min, p<0.001), cardiorespiratory fitness (B: 2.1 ml/kg/min, p<0.001), and sedentary time (B: -1.4 hours, p<0.001). Participants with a health club membership of >1 year had more favorable health outcomes, with a smaller waist circumference (men, B: -4.0 cm, p = 0.04; women, B: -3.4 cm, p = 0.06), compared to non-members. CONCLUSIONS: Health club membership is associated with significantly increased aerobic and resistance physical activity levels and more favorable cardiovascular health outcomes compared to non-members. However, longitudinal, randomized controlled trials would be clearly warranted as cross-sectional data prohibits causal inferences.